Electroplating copper



Patented Feb. 13, 1951 ELECTROPLATIN G COPPER Donald A Holt, Niagara Falls, N. Y., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware N Drawing. Application February 28, 1946, Serial No. 651,042

15 Claims. 1

This invention relates to electroplating copper, and more particularly to the electroplating of copper from cyanide solutions.

Electroplated copper coatings are used extensively as undercoats for other metals, such as nickel and chromium, for the formation of smooth, bright finishes on base metals, such as iron, steel, zinc alloy and the like. Bright finishes may be obtained by buffing or poishing the copper undercoating before applying the top coating. Another more satisfactory method of obtaining such bright finishes is to employ addition agents in the plating baths from which the copper undercoatings are plated, and it is this second method with which the present invention is primarily concerned.

It is an object of the invention to provide an improved method for electroplating copper from cyanide copper solutions. A further object is an improved method for electroplating smooth, bright copper deposits from cyanide solutions, which deposits are especially well adapted for use as undercoats in subsequent plating operations. A sti l further object is the provision of improved addition agents for cyanide copper plating baths which overcome the deleterious effects of the ordinary organic contaminants in such baths and permit the obtainment of bright, pitfree, adherent copper deposits which may be readily coated with electrodeposits of other metals. The above and still further objects will be apparent from the following description of the invention.

The above objects may be accomplished in accordance with my invention by adding small amounts of certain non-heterocyclic quaternary ammonium compounds, either alone or in combination with sma l amounts of certain betaine type compounds, to cyanide copper plating baths. I have discovered that the use of such compounds, or combinations of compounds, effects substantial improvements in plating operations from cyanide plating baths and greatly facilitates the obtainment of copper deposits which are pit-free and bright. The extent of the brightening or the anti-pitting action obtained will depend upon the particular compound or combination of compounds employed and also upon the other ingredients of the plating bath and the temperature and conditions under which plating is carried out.

The quaternary ammonium compounds which are suitable for use in accordance with the invention are the non-heterocyclic quaternary ammonium compounds which have four hydrocar- Icon radicals directly attached to a pentavalent nitrogen atom. In specifying that such compounds are non-heterocyclic, I do not mean that only acyclic compounds are suitable, since the preferred compounds include a benzene radical in their structure. Although certain cyclic compounds are preferred, none of the suitable compounds are heterocyclic; on the contrary, any ring structure present in such compounds must be homocyclic. The preferred compounds have the formula:

( 0 a) aElYL-X wherein R may be a methyl, an aryl substituted methyl, or an aryl radical and X may be a halogen atom or the hydroxyl radical. Of the preferred group of compounds, trimethyl benzyl ammonium hydroxide, trimethyl phenyl ammonium hydroxide and the corresponding halides, and particularly the chlorides, are especially well suited for use in practicing the invention. The sulfates of such hydroxides and other salts are also suitable but are not readily available.

To be especially effective, the non-heterocyclic quaternary ammonium compound should be soluble to a substantial extent in the cyanide copper plating baths and be reasonably stable under the conditions of operation. While some of the quaternary ammonium compounds which come within the broad class indicated above are not very soluble in these plating baths, they are soluble to such an extent that substantial brightening or anti-pitting action will result from their presence. Certain of the compounds, e. g., the tetra alkyl quaternary ammonium hydroxides and particularly those containing an alkyl group of more than one carbon atom, tend to decompose in the baths under plating conditions and for that reason their use is not preferred. However, it is possible by periodically replen shing the baths to employ effectively compounds which so decompose so long as decomposition does not occur at an excessive rate. Thus, tetramethyl ammonium hydroxide and its corresponding halides may be used effectively even though they tend to decompose at the plating temperatures normally employed, since by periodically replenishing the baths excellent copper deposits may be obtained.

As indicated above certain of the non-heterocyclic quaternary ammonium compounds are more effective than others, the most effective being trimethyl benzyl ammonium chloride and trimethyl phenyl ammonium chloride. These chlorides are preferred over the corresponding hydroxides primarily because they are more readily available. The plating baths in which they are to be used are strongly alkaline, and it may be that the above halides exist in the plating baths in the form of their corresponding hydroxides. However, since the hydroxides corresponding to the above chlorides are themselves strongly alkaline, it is possible that when the halide is added. to the plating bath substantial concentrations of both the halide and the hydroxide may be present. Accordingly, it should be understood that insofar as the present invention is concerned, the quaternary ammonium hydroxides and their corresponding salts, such as the sulfates, and particularly the halides, are to be regarded as equivalents regardless of which may actually be added to the plating bath.

When non-heterocyclic quaternary ammonium compounds are used which are not very soluble in the baths they should be used only in quantities which are not substantially in excess of the solubility of the compounds in the bath, since large amounts of undissolved compounds should be avoided.

The betaine type compoundsv which may be used in combination with the above quaternary ammonium compounds in practicing my invention are. derivatives of the simple alpha, beta and gamma betaines, which have the following structural formulae, wherein R stands for an alkyl radical, e. g., methyl, ethyl, etc., or a modified alkyl radical, e. g., hydroxyethyl and the like.

Gamma betaine The above simple betaines are not all suitable for use in my improved combinations of addition agents. The suitable betaines are those which have at least one acyclic hydrocarbon radical containing from to 20, preferably 10-16, carbon atoms. The acyclic hydrocarbon radical may be a straight or branched chain and may be either saturated or unsaturated. It may or may not be modified by the inclusion therein of radicals or groups, such as hydroxyl, amino and the like. These hydrocarbon radicals are substituted either for one of the alkyl groups on the nitrogen atom or for one of the hydrogen atoms on the alkylene group in the betaine, or both. For example, suitable betaines are trimethyl-C-cetyl alpha. betaine and trimethyl-C-cetyl beta betaine which have the following formulae:

CH3 CusHsa CH3 m aa QHr-N-CHC=O CH3N-CHOHz-C=O Ca .-.o Ca l.. o l Dimethyl-N-cetyl Dimethyl-N-stenyl alpha betaine alpha betaine In the N-stenyl betaine shown above the term stenyl is used to designate a mixture of essentially C16 and C18 carbon length chains with some C12, C14 and C20 carbon length chains also present. Thus, the N-stenyl betaine is a mixture of betaines having substituted hydrocarbons of the nature indicated by the above defination of the term stenyl. The preparation of the above N-stenyl and similar betaines is described in Downing et al., U. S. Patent 2,129,264. It is to be understood that in the various betaines utilized in this invention the methyl groups attached to the nitrogen atom in the above formulations may be replaced by other alkyl groups which may contain more or less than 12 carbon atoms. For example, in the N-stenyl betaine shown above, the two methyl groups may be replaced by other alkyl or modified alkyl groups, such as ethyl, propyl, hydroxyethyl and the like.

Various of the betaines which may be used to practice my invention are listed below by way of illustration:

di(beta -hydroxyethyl) -C-cetyl alpha 0 Methyl-N-distenyl alpha betaine Dimethyl-N-stenyl-C-cetyl beta betaine Dimethyl-N-decyl, beta-hydroxy gamma betaine Dimethyl-N-heptadecyl alpha betaine Dimethyl-N-octadecyl-C-methyl alpha betaine Dimeth-yl-N-octadecyl beta betaine Dimethyl-N-octadecyl, beta-hydroxy gamma betaine DimethyLN-lauryl alpha betaine Of the various betaines which may be used, I prefer to employ trimethyl-C-cetyl alpha betaine, trimethyl-C-decyl alpha betaine and dimethyl- N-lauryl alpha betaine. In particular, I prefer to employ as addition agents combinations of trimethyl benzyl ammonium hydroxide or a corresponding halide, such as the chloride, with trimethyl-C-cetyl alpha betaine, trimethyl-C-decyl alpha betaine or dimethyl-N-lauryl alpha betaine, or combinations of the above betaines with trimethyl phenyl ammonium hydroxide or a corresponding halide. Although producing excellent results in such combinations, trimethyl phenyl ammonium hydroxide and its halides are not as readily available as the corresponding trimethyl benzyl ammonium chloride in view of which I prefer to employ combinations involving the latter.

The following examples illustrate further the use of the above addition agents in accordance with the invention. In the, first 7 examples, the following types of plating baths were used.

Sodium Bath Potassium Bath KOH Free NaCN In all of the examples, electrolytic cathode copper was employed as the anode and the copper was plated on steel cathodes. The ratio of anode surface to cathode surface was 2:1.

Example 1 In this example, a 37% aqueous solution of trimethyl benzyl ammonium hydroxide was employed as the addition agent using stationary cathodes.

Plating Addition Amp.

Agent Z per Time, Results Pt./gal. Sq. Ft. min.

0 78-80 12 45 semi-b1'ightpitted 0.0042 78-80 12 45 Do. 0.0084 78-80 12 45 brightpitting reduced.- 0. 0127 78-80 12 45 brilliant-pitting greatly reduced. 0. 0254 78-80 12 45 brtilliantonly slight pit- Substantially the same results were obtained using trimethyl benzyl ammonium chloride as addition agent in both the above sodium and potassium baths.

Example 2 In this example, trimethyl phenyl ammonium iodide was employed as the addition agent using stationary cathodes. The agent was added in an amount corresponding to 0.11 oz. per gallon and copper was plated from the sodium type bath at a temperature of 79 C. employing a current density of 12 amperes per square foot for periods of 45 minutes. An excellent bright deposit of copper was obtained when using the addition agent which showed only a small amount of pitting, whereas in a similar experiment carried out in the absence of the addition agent, but otherwise under identical conditions, the copper deposit was relatively dull and badly pitted.

Example 3 In this experiment,,a solution of tetramethyl ammonium iodide was employed as the addition agent and the plating was carried out using stationary cathodes. The current density and plating time were the same as in Example 1.

Addition Agent i g Results Ptjgal.

0 78 badly pittedsemi-hright. 0. 0423 78 pitting \vorsebrighter deposit. 0. 0034 80 pittint roduced leposit much brighter. 0. 0845 79 only slight pitting-lustrous deposit Example 4 Substantially the same results were obtained using trimethyl benzyl ammonium chloride in place of the hydroxide in both the above sodium potassium baths.

The use of the above betaine type compounds as addition agents for cyanide copper plating baths is disclosed in Holt U. S. Patent 2,255,057. Those betaines, while being very effective antipitting agents, possess the distinct disadvantage of leaving a film on the copper deposits which is difiicult to wash off. Work plated in baths containing betaine addition agents alone exhibit a phenomenon called water-breaking, by which it is meant that such deposits when removed from the plating bath do not shed Water smoothly, i. e., are not free-rinsing. The water tends to break on the surface as a result of the film left thereon.

The presence of such films is highly objectionable in subsequent plating operations and by observing whether a copper deposit water-breaks or is free-rinsing, it is possible to determine readily whether or not the deposit may be satisfactorily plated, e. g., with nickel, in a subsequent plating operation. I have discovered that the tendency of copper deposits plated out in baths containing a betaine addition agent to waterbreax may be completely eliminated by the presence of suitable amounts of a non-heterocyclic quaternary ammonium compound of the type indicated above. The action of those quaternary ammonium compounds to prevent water-breaking and, therefore, to prevent the occurrence of objectionable betaine films on the copper deposits is illustrated in Examples 5, 6 and 7.

Example 5 The data tabulated below were obtained in plating operations substantially identical with those employed in Example 4. In the table, Agent A represents a 37% solution of trimethyl benzyl ammonium hydroxide and Agent B a solution of trimethyl-C-cetyl alpha betaine.

Substantially the same results were obtained using trimethyl benzyl ammonium chloride in both the above sodium and potassium plating baths.

Example 6 The data tabulated below were obtained using stationary cathodes. The plating periods were of minutes duration and the current density 12 amperes per square foot. In the table, Agent A represents trimethyl phenyl ammonium iodide and Agent 13 a 25% solution trimethyl-C-cetyl alpha betaine.

Pint Used per Gallon T p- C. 1 Results Agent A Agent 13 6 Results Agent A Agent 13 0 0 0. 0127 0 80 semi-brightbadly pitted. L 02./gnl. Pt./gal. O. 0127 0.0011 79 brilliant-slight pitting. 0 0 79 pitted badly. 0. 0127 0.0021 80 brilliantvery slight pitting. 0.11 O 80 pitting reducedfrec rinsing.

80 brilliant-no pitting. 0.11 0.0021 80 no pitting-free rinsing.

Substantially the same results were obtained using the above in both the above sodium and potassium baths.

Example 7 The data tabulated below were obtained in plating runs employing stationary cathodes and using as Agent A a 37% solution of trimethyl bfenzyl ammonium hydroxide and as Agent B Practically identical results were obtained using trlmethyl benzyl ammonium chloride in place of the hydroxide in both the above sodium and potassium plating baths.

Relatively small quantities of the above nonheterocyclic quaternary ammonium compounds are effective brighteners and anthpitting agents,

although the anti-pitting action is usually less marked than the brightening action. Quantities as low' as 0.01 ounce per gallon will generally have a noticeable brightening action, although with certain compounds it may be necessary to employ larger quantities before beneficial action is noticeable. I prefer to employ 0.15 to 0.5 ounce per gallon. Still larger amounts may be used with good results so long as the non-heterocyclic quaternary ammonium compound used is sufilciently soluble in the bath, e. g.. quantities as high as 1 ounce per gallon maybe used in certain instances. Generally, there is no particular advantage derived from the use of more than about 1 ounce per gallon.

The above quantities of the non-heterocyclic quaternary ammonium compound apply whether the compound is used alone or in combination with a betaine compound. In such combinations, the betaine compound may be used in amounts ranging from 0.005 to 0.2 ounce per gallon, the preferred amounts being 0.01 to 0.1 ounce per gallon.

The present addition agents and combinations of addition agents are particularly well-suited for use in cyanide copper plating baths intended for use in the so-called high efiiciency plating operations, i. e., in plating operations carried out under such conditions that the cathode efficiency is substantially 100% with little or no visible evolution of hydrogen at the cathode. Such high efliciency plating operat ons generally involve the use of plating baths containing the double copper alkali metal cyanide in high concentrations, as... in concentrations equivalent to a copper cyanide (CuCN) concentration of 6 to 20 ounces per gallon. The bath will contain little or no free alkali metal cyanide, i. e., 0 to 3 ounces and preferably 0.3 to 0.9 ounce per gallon determined using a neutral KI indicator and a high concentration af alkali metal hydroxide, e. g., 1 to 8 ounces per gallon. The plating operation will be carried out at a temperature ranging from 60 C. up to the boiling point of the bath. Temperatures of 70 to"85 C. are generally preferred. However, if a pit-free deposit is the chief object and. a high degree of brightness is of minor importance, temperatures inexcess of 85.may be employed satisfactorily. This particular type of high-speed, high-efficiency copper plating is il-'- lustrated by the foregoing examples.

The addition agents. of the invention also may be used in other types of cyanide copper plating baths. For example, under suitable conditions of operation baths of lower cyanide content may be used whether or not such baths contain plating ingredients other than those illustrated above. Thus, cyanide copper plating baths of the Rochelle salt type may be used with improved results employing the present addition agents if operated under suitable conditions. In such low cyanide concentration baths, the plating should be carried out under such conditions that high cathode efficiency is realized, i. e., under conditions such that no visible evolution of hydrogen occurs at the cathode. As a general rule, the temperature of the plating bath should be within the range 50 to 70 C. using a current density of 5 to 36 amperes per square foot with little or no free alkali metal cyanide being present. In low concentration cyanide baths containing no Rochelle salt, the temperature will generally be within the range of '75 to 85 C. with a current density of about 3.5 to 20 amperes per square foot.

In mentioning specific conditions in connection with the various types of cyanide copper plating baths, it is intended merely to illustrate generally suitable conditions since the proper temperature, proper current density and proper concentrations of the various normal bath ingredients can be readily determined and understood by those skilled in the art of copper plating. The use of my invention in cyanide plating baths of the low concentration type is illustrated further by the following examples.

In this example, a plating bath of the follow.- ing composition was employed:

Ounces per gallon Copper cyanide 3.5 Sodium cyanide 4.5 Rochelle salt 4.0 Sodium carbonate 4.0 Free sodium cyanide 0.75 Caustic soda to give a pH of 12.6

In the experiment, the steel cathode was subjected to a constant reciprocal horizontal motion at a linear velocity of about 12 feet per minute. The temperature was about C. and the current density 5 amperes per square foot. Using no addition agent a semi-bright deposit was obtained, whereas when 0.0127 pt. per gallon of a solution prepared by mixing 3.7 pounds of a 61 solution of trimethyl benzyl ammonium chloride with 1.5 pounds of water and 1 pound of a 25% solution of trimethyl-C-cetyl betaine was added, a substantially brighter and more uniform copper deposit was obtained.

Example 9 In this example, a plating bath of the following composition was employed:

Ounces per gallon Copper cyanide 3.5 Sodium cyanide 4.5 Sodium carbonate 4.0 Free sodium cyanide'; 0.75

15 Caustic soda to give a pH of 12.6

A moving cathode was employed as in Example 8 I and the plating was carried out at 80 C. with a current density of 3.5 amperes per square foot.

In one run no addition agent was added and in a second run 0.0127 pt. per gallon of the addition agent mentioned in Example 8 was employed. In the absence of the addition agent, dull matte deposits were obtained, whereas when the addition agent was present bright highly uniform deposits were obtained.

The foregoing examples illustrate the use of my improved addition agents to inhibit or prevent pitting and to give bright copper deposits. Use of the above non-heterocyclic quaternary ammonium compounds or combinations thereof withv the above betaines has the further important advantage in that they eliminate the deleterious action of the ordinary organic contaminants which are invariably present in cyanide copper plating baths. It is well-known that the presence of such contaminants is very harmful and result in the formation of blotchy copper deposits and under some circumstances deposits which are distinctly spongy in nature. By the use of the present addition agents, particularly combinations of the non-heterocyclic quaternary ammonium compounds with suitable betaines. excellent dense conper deposits which are bright in appearance and which are entirely free from pits and blotches may be readily obtained in cyanide copper plating baths containing initially the ordinary or anic contaminants generally present in such baths. A further advantage in employing the present combinations of addition agents is that the brightening effect produced by the two constituents of a combination is substantially greater than the sum of the effects of the two constituents when used alone. Thus, each constituent in the combination ap ears to enhance the brightening action of the other constituent.

The alkali metal sulphocyanides used as ingredients in the baths of Examples 1 to 7 are themselves brightening agents and are disclo ed as such in Wernlund et a1. U. S. Patent 2,287,654.

The above sulphocyanides, however. do not prevent pitting and in high-speed, high-efficiency plating operations, the brightening action is not as effective as desired. When practicing the present invention, such sulnhocyanides may be omitted entirely from the plating baths. However, I have found that best over-all results are obtained in baths of the tyne illustrated in the Exam les 1 to '7. which baths contain an alkali metal sulphocvanide as well as an addition a ent of the present invention. I prefer that the a kali. metal sulphocyanide content in such baths be about 1 to 8 and preferably about 2 ounces pe gallon.

In practicing the invention, I have found it to be very satisfactory and practicable to employ a mixture of a suitable betaine compound with a suitable non-heterocyclic quaternary ammonium co pound as the agent which is added to the plating bath. One of the most effective of such mixtures is an aqueous solution prepared by mixing together 3.7 parts of a 61% aqueous solution of tr methyl benzyl ammonium chloride, 1 part of a solution of a trimethyl-C-cetyl alpha betaine and 1.5 parts by weight of water. Also highly effective is a 1 to 1 mixture by weight of a 61% solution of trimethyl benzyl ammonium chloride and a 25% solution of trimethyl-Cdecyl alpha betaine. In place of the trimethyl benzyl ammonium chloride in the above mixtures, a corresponding quantity of trimethyl phenyl ammonium halide is also highly effective and in any of the above specific mixtures stoichiometric amounts of corresponding quaternary ammonium hydroxides or suitable salts thereof may be employed with good results. In such preparations, the proportion of the quaternary ammonium compound to the betaine compound will vary de-- pending upon the particular compounds used, but generally will be in the range of 1.5 to 15 parts of the quaternary compound per one part of the betaine compound on a basis. In the above specific combinations mentioned, I prefer using about 8 to 10 parts by weight of trimethyl benzyl ammonium chloride per 1 part of trimethyl-C-cetyl alpha betaine and 2.3 to 2.6 parts of the same chloride for 1 part of trimethyl-C- decyl alpha betaine. The quantity of water employed in any of these mixtures is not critical,

but it is preferable to use sufiicient water to dismetal cyanide solution which contains 0.01 to 1 ounce per gallon of a compound of the formula:

s)sE1}IX wherein, R is a radical selected from the group consisting of methyl, benzyl and phenyl radicals, and X is selected from the group consisting of halogens and the hydroxy radical.

2. A copper plating process comprising electrolyzing an aqueous, alkaline copper alkali metal cyanide solution which contains 0.15 to 0.5 ounce per gallon of a compound of the formula:

wherein R is a radical selected from the group consisting of methyl, benzyl and phenyl radicals, and X is selected from the group consisting of halogens and the hydroxy radical.

3. A copper plating process comprising electrolyzing an aqueous, alkaline copper alkali metal cyanide solution which contains 0.15 to 0.5 ounce per gallon of trimethyl benzyl ammonium chloride. l

4. A copper plating process comprising electrolyzing an aqueous, alkaline copper alkali metal cyanide solution which contains 0.15 to 0.5 ounce per gallon of a trimethyl phenyl ammonium halide.

5. A copper plating process comprisinr electrolyzing an aqueous, alkaline copper alkali metal cyanide solution which contains 0.005 to 0.2 ounce of a betaine having at least one acyclic hydrocarbon radical of 10 to 16 carbon atoms and 0.01 to 1 ounce per gallon of a compound of the formula:

( C H aEN-X wherein R is a radical selected from the group consisting of methyl, benzyl and phenyl radicals, and X is selected from the group consisting of halogens and the hydroxy radicals,

6. .A copper plating processcomprising' electrolyzing an aqueous, alkaline copper a kali metal cyanide solution which contains 0.01 to 0.1 ounce per gallon of a betaine having at least one acyclic hydrocarbon radical of 10 to 16 car bon atoms and 0.15 to 0.5 ounce per gallon of a compound of the formula:

wherein R is a radical selected from the group consisting of methyl, benzyl and phenyl radicals,-and X is selected from the group-consisting of halogens and the hydroxy radical.

'7. A copper plating process comprising electrolyzing an aqueous, alkaline copper alkali metal cyanide solution which contains 0.01 to 0.1 ounce per gallon of a betaine having at least one acyclic hydrocarbon radical of to 16 carbon atoms and 0.15 to 0.5 ounce per gallon of trimethyl benzyl ammonium chloride.

8. A copper plating process comprising electrolyzing an aqueous, alkaline copper alkali metal cyanide solution which contains 0.01 to 0.1 ounce per gallon of a betaine having at least one acyclic hydrocarbon radical of 10 to 16 carbon atoms and 0.15 to 0.5 ounce per gallon of a trimethyl phenyl ammonium halide.

9. A-copper plating process comprising electrolyzing an aqueous, alkaline copper alka i metal cyanide solution which contains 0.01 to 0.1 ounce per gallon of trimethyl-C-cetyl alpha betaine and 0.15 to 0.5 ounce per gallon of trimethyl benzyl ammonium chloride.

10. A copper pating process comprising elecytrolyzing an aqueous, alkaline copper alkali metal cyanide solution which contains 0.01 to 0.1 ounce per gallon of trimethyl-C-decyl alpha betaine and 0.15 to 0.5 ounce per gallon of trim'ethyl benzyl ammonium chloride.

11. A copper plating process comprising electrolyzing an aqueous, alkaline copper alkali metal cyanide'solution which contains 0.01 to 0.1

ounce per gallon of trimethyl-C-cetyl alpha betaine and 0.15 'to 0.5 ounce per gallon of a trimethyl phenyl ammonium halide.

12. A composition of matter useful as a brightening and anti-pitting agent in aqueous alkaline copper alkali metal cyanide electroplating baths, which contains as substantially the only brightening and anti-pitting ingredients a betaine having at least one acyclic hydrocarbon radical of 10 to 16 carbon atoms and a compound of the formula:

(CH3) EN-X 1 I '12 wherein R is a' radical selected from the group consisting'of methyl, benzyl and phenyl radicals, and X is selected from the group consisting of halogens and the hydroxyl radical, said ingredients being present in the ratio of 1.5 to 15 parts by weight of said compound of the above formula per one part of said betaine.

13. A composition of matter useful as a brightening and anti-pitting agent in aqueous alkaline copper alkali metal cyanide electroplating baths, which. contains as-substantially the only brighteningand anti-pitting ingredients trimethyl-C- cetyl alpha betaine and trimethyl benzyl ammonium chloride in the ratio of 1.5 to 15 parts-by weight of said chloride per one part of said betaine.

14. :A composition of matter useful as a brightening and anti-pitting agent in aqueous alkaline copper alkali metal cyanide electroplating baths, which contains assubstantially the only brightening and anti-pitting ingredients trimethyl-C- decyl alpha betaine-and trimethyl benzyl ammonium chloride'in the-ratio of 1.5 to 15 parts by weight of saidchloride per one part of said be taine.

15. A composition'of matter useful-as a brightening and anti-pitting agent in aqueous alkaline copper alkali metal cyanideelectroplating baths, which contains 'as substantially the only brightening and anti-pittingingredients .trimethyl-C- cetyl alpha 'betaine and a trimethyl phenylammoniumhalide in theratio of 1.5 to 15 parts by Weight of said halide "perone part of said betaine.

DONALD -A. HOLT.

REFERENCES CITED The following references are of record in the file of this patent: V

UNITED STATES PA'I'ENTS Number Name Date 1,536,859 Humphries May 5, 1925 2,195,454 Greenspan Apr. 2, 1940 2,255,057 Holt Sept. '9, 1941 2,315,802 Lind Apr. 6, 1943 2,474,092 Liger June 21, 1949 FOREIGN PATENTS Number Country 1 Date 601,036 Germany 1 Aug. 7, 1934 OTHER REFERENCES Metal Industry, Nov. 10, 1944, page 298, 299 Mathers et al., Transactions of Electrochemical Society, vol. 78 -(1940), pp. 345-7. 

1. A COPPER PLATING PROCESS COMPRISING ELECTROLYZING AN AQUEOUS, ALKALINE COPPER ALKALI METAL CYANIDE SOLUTION WHICH CONTAINS 0.01 TO 1 OUNCE PER GALLON OF A COMPOUND OF THE FORMULA: @SP (CH3)3=N-X @SP WHEREIN R IS A RADICAL SELECTED FROM THE GROUP CONSISTING OF METHYL, BENZYL AND PHENYL RADICALS, AND X IS SELECTED FROM THE GROUP CONSISTING OF HALOGENS AND THE HYDROXY RADICAL. 